The value of the critical temperature Tc and isotope coefficient a could be greatly
affected by a number of factors. Among them are the presence of magnetic impurities, non-magnetic impurities, disorder and defects. Following previous calculation
of the critical temperature and isotope effect by Singh and Kishore (P. Singh and R.
Kishore, J. Supercond. 8, 9 (1995)), Singh et al. (S. P. Singh, R. K. Pandey, and P.
Singh, J. Supercond. 9, 277 (1996)), Openov (Phys. Rev. B 58, 9468 (1998)) and
Openov et al (Phys. Rev. B 64, 12513 (2001)) we have considered the effect of disorder (defect) on the superconducting transition temperature Tc and isotope coefficient
a with in the BCS model. An expression for Tc and a as a function of potential and
spin-flip scattering rates is derived by means of Green’s functions technique. This is
done with the introduction of the matrix Green function in the Nambu representaarbitrary tion. Thedegree expression of anisotropy for In (^of ) the andsuperconducting (— ) is obtainedorder for a parameter superconductor , ranging with from an
isotropic s-wave to d-wave and including anisotropic s-wave and mixed (s+d)-wave
as to particular where rcases is the . The totaluniversal relaxation dependence time) andof (^(^) on ) on 6 or tp ip (afor factor a given proportional value of
X (a coefficient for anisotropy of the order parameter) is shown in different plots for
different cases.

Description:

A Thesis Submitted to the School of Graduate Studies of Addis Ababa University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Physics.